Winter Squash

Planted in late spring, grown in summer, harvested in fall, then stored during winter, winter squash occupies a unique niche in the home garden. This member of the Cucurbitaceae (cucumber or gourd) family includes many species and varieties, some familiar, many colorful with unusual shapes. All are harvested after their outer shell becomes hard. 

Wide Selection

• Acorn squash has a recognizable acorn shape, dark green, with yellow-orange flesh.
• Banana squash grows in a torpedo shape with dense orange flesh inside pale orange, pink, yellow, or blue skin.
• Kabocha bears whitish splashes on bluish green skin on a mostly round, thick but somewhat squat shape; flesh is very sweet.
• Buttercup resembles kabocha with a squat shape, green skin, and orange flesh.
• Butternut has a bulbous base, pale orange skin, and darker orange, sweet flesh.
• Delicata has a yellow, cylindrical shape with thin green stripes and yellow flesh.
• Sweet Dumpling lives up to its name with a tiny 3-5 in. size and a speckled cream-colored, indented shell marked with dark green ribs.
• Hubbard squashes are among the largest with a bumpy, orange, blue, or green exterior and orange flesh.
• Spaghetti squash resembles a yellow football with golden flesh that separates into long strands.
• Turbans are one of the most colorful with a variable round, reddish orange base topped with an orange-white-and green cap.
• Numerous named varieties of each type are available in seed catalogs. Look for varieties resistant to pests and diseases.

Seeding Squash

• Amend soil with compost to improve texture and drainage; mix in a slow-release organic fertilizer before planting.
• Plant after the last April frost date but no later than June to allow 85-110 days of summer sun before harvesting.
• Start seeds indoors in late March or early April; wait to transplant outdoors until the soil warms.
• Direct sow after soil warms to 60 degrees, placing 4-6 seeds in a circle about 10 in. in diameter, ½-1 in. deep in a moist hill (low mound) of soil.
• Allow 6-10 ft. or farther apart between hills, depending on varieties. Consult information on seed packets for expected growth of bush types or vining squashes with stems 5-20 ft. long.
• Thin all but 2-3 of the sturdiest seedlings after they develop their first 2 sets of true leaves.
• Protect seedlings from birds by spreading loose netting over foliage until leaves enlarge and become prickly.

Summer Growth

• Allow soil surface to dry between waterings but maintain even moisture to 12 in. deep.
• Wait until morning If leaves look a little wilted in afternoons to see if the plants perk up. It is common for large-leaved vegetables to wilt a little in hot afternoon sun. Check soil moisture before watering.
• Watch for powdery mildew on foliage and remove any infected debris. This disease is more prevalent in warm, dry inland areas than near the coast. Some varieties are resistant.
• Watch for cucumber beetles and squash bugs or prevent them by using row covers when plants are very young; check regularly to be sure that none are trapped underneath netting. Handpick bugs and destroy any eggs on the undersides of leaves.
• Remove row covers when flower formation begins so that bees can begin pollination.  
• Stay alert for presence of bees if you have blossoms and no fruit. In the absence of a healthy bee population, hand pollination may be needed. Use a cotton swab to carefully transfer pollen from a newly opened male flower to female flowers. (Male flowers have narrow stems; female flowers are swollen at the base).
• Watch for female flowers to emerge. Several male flowers form earlier and lower on vines.

Harvesting, Curing, and Storing

• Wait for squashes to fully ripen before harvesting,  70-110 days or longer. Rinds will be hard and stems will turn brown and resistant to puncture by a fingernail. They generally become even-colored although the side touching the soil may have a lighter hue.
• Use a sharp knife or pruners to harvest, leaving 1-3 in. of stem attached, but do not lift by the stem to avoid breaking it. Without the stem, squashes do not store well.
• Move squashes away from wet soil to a dry, warm area for 1-2 weeks to cure before storage. They can remain stored on the stem in the garden as long as they are not sitting on wet or damp ground and there is not a hard freeze.
• Seek out optimal conditions at 80-85 degrees for 1-2 weeks to cure for long-term storage. Good air circulation is needed.
• Store in a single layer in a dry, fairly cool area, ideally at 50-60 degrees. Once cured, squashes can be stored for up to 6 months although some types maintain quality for only 2-3 months.

Additional Information

• Sonoma County Master Gardener Vegetable Planting Summary
• https://sonomamg.ucanr.edu/Food_Gardening_with_Less_Water/
• http://ipm.ucanr.edu/home-and-landscape/squash/index.html
• http://ipm.ucanr.edu/home-and-landscape/squash/cultural-tips/

February 2022